1. Field of the Invention
The present invention relates to a fuel injection system for air-compressing, spontaneous ignition, reciprocating piston internal combustion engines which have a fuel injection pump and an injection nozzle for each cylinder unit. At least one parameter characteristic of the injection process, such as beginning of injection, end of injection, and duration of injection, is adapted to be regulated by at least one electromagnetic control valve per cylinder unit. Each control valve preferably controls a low-pressure line, especially a discharge line, which is provided on the high-pressure side of the fuel injection pump. Each control valve can be controlled by an electrically operating data processor by means of a control pulse as a function of characteristic operating parameters of the internal combustion engine. If necessary or desired, a further mechanically operated adjustment member can be provided for controlling the fuel injection system.
2. Description of the Prior Art
A fuel injection system of the aforementioned general type having an electromagnetic control valve and a data processor is known from German Offenlegungsschrift No. 20 26 665. In this system, each cylinder unit is provided with an electromagnetic control valve which controls a discharge line on the pressure side of the fuel injection pump. The discharge line can be opened by the control valve, especially to regulate the end of injection of the fuel injection system. In order with such a system to be able to compensate for deviations of the transmission characteristics of the electromagnetic control valves as caused by wear and operation, German Offenlegungsschrift No. 20 26 665 proposes determining the actual value control times of a single electromagnetic control valve, and controlling the remaining electromagnetic control valves while taking into consideration the comparison of the actual value control times of this first electromagnetic control valve and the desired value control times of the electrically operating data processor. However, since the transmission characteristics of the electromagnetic control valves can vary greatly due to the specific formation of wear, deviations of all of the electromagnetic control valves of the cylinder units of the internal combustion engine can be only very unsatisfactorily compensated for with such a system, so that a satisfactory operation of an air-compressing, spontaneous ignition, reciprocating piston internal combustion engine having such a fuel injection system is not possible, especially with a view toward the very high fuel injection pressures which are continuously being aimed for, and the correspondingly very short durations of injection.
An object of the present invention therefore is to improve a fuel injection system of the aforementioned general type in such a way that deviations of the transmission characteristics of the electromagnetic control valves of the system can be compensated for, and the control time points of the electromagnetic control valves determined by the electrically operated data processor can be precisely and accurately set.